Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CASE OR-6578
211296
SILOXY - ALUMINOXANE COMPOSITIONS
This process relates generally to soluble
aluminoxane derivatives and more particularly to siloxy-
aluminoxane compositions obtained by the reaction of alkyl-
s disiloxanes and aluminoxanes which, in the presence of
metallocenes, form catalytically active compositions for
olefin polymerization.
U.S. Patent No. 3,740,384 discloses that the
addition of dihydroxysiloxane to non-metallocene organo-
zirconium catalyst systems in the absence of aluminoxanes
gave improved catalyst activity in olefin polymerization.
Likewise, U.S. Patent No. 4,945,076 describes the improved
activity in olefin polymerization which is obtained by the
addition of dihydroxysiloxane to a catalyst system consisting
of a metallocene and an aluminoxane. The resulting ethylene
polymer is said to have acquired a lower melt flow rate (MFR)
than those produced without the silicon compound. U.S.
Patent No. 5,034,549 discloses that a preformed catalyst
component is obtained by the reaction of dihydroxysiloxane or
silicon diol with a zirconocene. The patent further alleges
that this catalyst component, when used in conjunction with
methyl-aluminoxane, formed a good catalyst system for olefin
polymerization.
All the above mentioned disclosures describe the
use of alkoxy-silanes having Si-O-C bonds, silicon diols
having Si-OH bonds and dihydroxysiloxanes having both the
Si-O-Si and Si-OH bonds. The reagents used in the present
invention, namely alkyldisiloxanes, have only the Si-O-Si
bonds. The chemical reactivity of the alkyldisiloxanes is
significantly different from those of the silanols, silyl
ethers, silyl esters and hydroxy disiloxanes (1.
Comt~rehensive Oraanometallic Chemistry, Vol. 2, Chap. 9;
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21129~~
Pergamon Press, 1982: 2. Comprehensive Organic Chemistry,
Vol. 3, Chap. 13 Pergamon Press N.Y. 1979). Those skilled in
the art would appreciate the fact that silicon compounds
having Si-OH bonds generally undergo dehydration and conden-
sation reactions. These reactions are rarely observed in the
case of alkyldisiloxanes. Thus, one could not anticipate any
obvious similarity between the reactions of silanols, silyl
ethers and silyl esters compared to alkyldisiloxanes. In
fact one would not expect to isolate under similar condi-
tions, the same product described in U.S. Patent No.
5,034,549 by substituting an alkyldisiloxane for the
dihydroxysiloxane or silicon diol, as this would require the
breaking of Si-O bond which is more difficult than breaking
the Si0-H bond.
It has now been found that aluminoxanes will react
with alkyldisiloxanes to form novel, soluble siloxy-aluminum
compounds which, in combination with metallocenes, provide
olefin polymerization catalysts having very high activity.
In accordance with this invention there is provided
a siloxy-aluminoxane composition which is the reaction
product of an alkyldisiloxane and an aluminoxane where the
molar portions of aluminum to alkyldisiloxane are from 1:1 to
50:1.
Also provided is an olefin polymerization catalyst
comprising a metallocene of a transition metal and a siloxy-
aluminoxane composition which is the reaction product of an
alkyldisiloxane and an aluminoxane where the molar portions
of aluminum to alkyldisiloxane are from 1:1 to 50:1.
Preferred aluminoxanes for use in making the
siloxy-aluminoxane compounds are hydrocarbylaluminoxanes.
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2112965
Hydrocarbylaluminoxanes may exist in the form of
linear or cyclic polymers with the simplest compounds being a
tetraalkylaluminoxane such as tetramethylaluminoxane,
(CH3) zAlOAl (CH3) 2, or tetraethylaluminoxane, (CZHS) ZAlOAl (CZHS) 2.
The compounds preferred for use in olefin polymerization
catalysts usually contain 4 to 20 of the repeating units:
R
fAl-O~
where R is C,-C,o alkyl and especially preferred are methyl-
aluminoxanes (MAO). The methylaluminoxanes can contain some
higher alkyl groups to improve their solubility. Such
modified methylaluminoxanes are described, for example, in
U.S. Patent No. 5,157,008.
The aluminoxanes can be prepared as known in the
art by the partial hydrolysis of trialkylaluminum compounds.
The trialkylaluminoxane compounds can be hydrolyzed by adding
either free water or water containing solids, which can be
either hydrates or porous materials which have absorbed
water. Because it is difficult to control the reaction by
adding water per se, even with vigorous agitation of the
mixture, the free water is preferably added in the form of a
solution or a dispersion in an organic solvent. Suitable
hydrates include salt hydrates such as, for example,
CuS04~5H20, A12(S04)3~18H20, FeS04~7H20, A1C13~6H20, A1(N03)3~9H20,
MgS04~7H20, ZnS04~7H20, Na2S04~1OH20, Na3P04~12H20, LiBr~2H20,
LiCl~1H20, LiI~2Hz0, LiI~3H20, KF~2H20, NaBr~2H20 and the like
and alkali or alkaline earth metal hydroxides such as, for
example, NaOH~H20, NaOH~2Hz0, Ba (OH) 2~8Hz0, KOH~2H20, CsOH~1H20,
LiOH~1H20 and the like. Mixtures of any of the above
hydrates can be used. The mole ratios of free water or water
in the hydrate to total alkyl aluminum compounds in the
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2112965
mixture can vary widely, such as for example from 2:1 to 1:4
with ratios of from 4:3 to 1:3.5 being preferred.
Such processes for preparing hydrocarbyl-
aluminoxanes are described, for example, in U.S. Patent No.
4,908,463. The methylaluminoxanes contain varying amounts,
of from about 5 to 35 mole percent, of the aluminum value as
unreacted trimethyl-aluminum.
The alkyldisiloxanes for use in the invention have
alkyl groups which preferably contain from 1 to 20 carbon
atoms. The alkyldisiloxanes contain the Si-O-Si bond and are
substantially free of Si-OH or Si-O-C bonds. The alkyl
disiloxanes can contain mixed alkyl groups. Non-limiting
examples of alkyldisiloxanes include hexamethyldisiloxane,
hexaethyldisiloxane, tetramethyldisiloxane, and the like.
The siloxy-aluminoxane compositions can be prepared
by reacting the aluminoxane and alkyldisiloxane in an organic
solvent medium in molar portions of aluminum to alkyldi-
siloxane of from 1:1 to 50:1. Mixtures of aluminoxanes
and/or alkyldisiloxanes can be used in forming the composi-
tions. Any inert organic solvent can be used as the reaction
medium. Non-limiting examples of solvents include aliphatic
hydrocarbons such as pentane, isopentane, hexane, cyclo-
hexane, heptane, octane, decane, dodecane, hexadecane, octa-
decane and the like with those having carbon numbers of 5 to
10 being preferred and aromatic hydrocarbons such as benzene,
toluene, xylene, cumene and the like with those having carbon
numbers of 6 to 20 being preferred. Generally amounts of
solvent to provide a total concentration of reactants of from
10 to 30 wt. percent are used.
Preferred reaction temperatures range from about 25
to 90°C.
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CA 02112965 2004-04-27
The siloxy-aluminoxane compounds can be used in
combination with metallocenes to provide olefin
polymerization catalysts. Such metallocenes are well known
in the art and non-limiting examples include the
metallocenes described in published European patent
application No. 0 129,368 and U.S. Patent Nos. 5,017,714
and 5,026,798. Illustrative examples of such metallocenes
are bis(cyclopentadienyl)zirconium dimethyl,
bis(cyclopentadienyl)zirconium dichloride,
bis(cyclopentadienyl)zirconium monomethyl-monochloride,
bis(cyclopentadienyl)titanium dichloride,
bis(cyclopentadienyl)titanium difluoride,
cyclopentadienyl)zirconium tri(2-ethylhexanoate),
bis(cyclopentadienyl)zirconium hydrogen chloride,
bis(cyclopentadienyl)hafnium dichloride and the like.
The catalyst components are used in proportions
to provide mole ratios of transition metal atom to aluminum
atom of from about 0.0002:1 to 0.2:1 and preferably
0.0005:1 to 0.02:1. The catalyst components can be used in
solution or deposited on a solid support. The solid support
can be any particulate solid, and particularly porous
supports such as talc or inorganic oxides, or resinous
support material such as polyolefins. Preferably, the
support material is an inorganic oxide in finely divided
form.
Suitable inorganic oxide support materials which
are desirably employed include Group IIA, IIIA, IVA or IVB
metal oxides such as silica, alumina, silica-alumina and
mixtures thereof. Other inorganic oxides that may be
employed either alone or in combination with the silica,
alumina or silica-alumina are magnesia, titania, zirconia,
and the like. Other suitable support materials are finely
divided polyolefins such as finely divided polyethylene.
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211965
The catalysts are effective to produce olefin
polymers and especially ethylene polymers and ethylene/a-
olefin copolymers. Examples of olefins that can be
polymerized in the presence of the catalysts of the invention
include a-olefins having 2 to 20 carbon atoms such as
ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene,
1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene,
and 1-octadecene. Polymerization of ethylene or copolymer-
ization with ethylene and an a-olefin having 3 to 1o carbon
atoms is preferable. Such polymerizations may be performed
in either the gas or liquid phase (e.g. in a solvent, such as
toluene, or in a diluent, such as heptane). The polymer-
ization can be conducted at conventional temperatures (e. g.,
0° to 120°C.) and pressures (e. g., ambient to 50 kg/cm2)
using conventional procedures as to molecular weight
regulations and the like.
The invention is further illustrated by, but is not
intended to be limited to, the following examples.
The following examples were carried out under inert
atmosphere conditions, using Schlenk glassware and vacuum
line, in conjunction with a NZ-drybox. Solvents were
distilled using standard methods. Filtration and vacuum
distillation were done inside a NZ-drybox and distillates
were collected in a trap at -78°C. Disiloxanes were
purchased from Aldrich and used without further purification.
Aluminoxanes were obtained from stock solutions produced by
Ethyl.
Example 1
Solid methylaluminoxanes (MAO, 38 mmol A1) was
suspended in hexane (50 mL). The mixture was stirred at room
temperature (30 minutes). Hexamethyldisiloxane (HMDS, 4.7
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21129 fi 5
mmol) was then slowly added via syringe. After stirring for
16 hours, the mixture was filtered. The hexane solution was
then concentrated to dryness by vacuum distillation. The
resulting solid siloxy-MAO product contained 65% of the
initial aluminum value. Silicon-29 and proton NMR showed one
sharp singlet each for the siloxy group. Additionally, H-1
NMR showed the usual broad peak for methylaluminoxane in the
aluminum alkyl region. The sharp signals suggest a probable
end capping environment of the siloxy group in the MAO
structure.
Example 2
Solid MAO (122 mmol A1) was suspended in hexane
(300 mL) in a reaction flask. HMDS (60 mmol) was added via
syringe. The mixture was stirred for about 30 minutes at
room temperature and then heated to 70°C (oil bath) for
another 12 hours. The slurry was filtered and the filtrate
was concentrated to give a white solid material which
contained 67% of the initial aluminum value. Si-29 and H-1
NMR data are similar to those obtained for Example 1.
Example 3
Solid MAO (60 mmol A1) was placed in hexane (100
mL). To the slurry was added HMDS (75 mmol). The mixture
was magnetically stirred for about 20 hours and then
filtered. The filtrate was concentrated to give white
granular siloxy-MAO derivative.
The preceding Examples 1-3 showed that the
variation of HMDS concentration, reaction time and thermal
conditions did not significantly alter either the product
yield or the spectroscopic data of the resulting solid
siloxy-MAO derivative.
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2112965
Example 4
This preparation was done to investigate the effect
of a mixed solvent system, toluene/hexane. A toluene
solution of MAO (350 mmol A1) was placed in a reaction flask
and hexane (150 g) was added. The HMDS (90 mmol) was then
slowly added via syringe. The mixture was stirred for about
14 hours at room temperature. After filtration, the clear
liquid which contained 90% of the original aluminum value,
was concentrated to give a white solid siloxy-MAO product.
H-1 NMR data showed more sharp peaks overlapping
the usual MAO broad peak in the aluminum alkyl region, than
was seen in the alkane product.
Example 5
Solid MAO (30 mmol A1) was dissolved in toluene (20
mL) and then HMDS (5 mmol) was added. The reaction was
carried out as described in Example 1. The resulting solid
product contained 92% of the original aluminum value. H-1
NMR contained several singlet peaks buried under the usual
broad MAO peak.
Example 6
Solid MAO (75 mmol A1) was added to a toluene
solvent (50 mL). To this solution was then added HMDS
(30mmo1) from a syringe. The mixture was stirred at room
temperature for about 4 hours. The hexane (50 mL) was added
and the mixture was stirred for another 2 hours and filtered.
The filtrate was concentrated to dryness to give a solid
product which contained 85% of the initial aluminum value.
_ g _
21129~~
The H-1 NMR of the solid, hexane derived siloxy-MAO
product showed only one sharp singlet peak in the aluminum
alkyls region regardless of the concentration of HMDS. By
contrast, similar spectra for the solid, MAO in toluene
derived products showed several sharp singlet peaks in the
aluminum alkyls region. Furthermore, as the molar ratio of
HMDS increased the number of singlet peaks attributable to
the siloxy derivatives increased. The reason for this
unequivocal solvent effect is not known.
l0 Example 7
Solid MAO (75 mmol A1) was dissolved in toluene (50
mL). To this solution was added HMDS (75 mmol). The mixture
was stirred at room temperature for about 20 hours. Hexane
(50 mL) was added and then the mixture was stirred for
another 4 hours. After filtration and concentration, the
resulting solid siloxy-MAO compound contained 88% of the
original aluminum value.
H-1 NMR of the solid compound showed several
singlet peaks (Me3Si0) buried under the broad MAO peaks.
The starting material in the above described
reactions was solid MAO. This was obtained by removal of
toluene from the MAO solution via vacuum distillation. For
commercial purposes, it is desirable to avoid extra
processing requirements. The following examples describe the
formation of siloxy-MAO compositions directly from the
initial toluene solution of MAO.
Example 8
A MAO solution in toluene (271 mmol A1, 78 g of a
9.4% A1 by weight solution) was placed in a reaction flask.
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2~~~~s5
HMDS (68 mmol) was slowly added at room temperature. The
mixture was stirred for about 12 hours and then heat (oil
bath, 80°C) was applied for about 2 hours. The mixture was
filtered and the filtrate was found to contain 92% of the
original aluminum value.
This siloxy-MAO solution was found to be more
active, compared to the original MAO solution, in an ethylene
polymerization test (Table 1).
Example 9
To a solution of MAO in toluene (300 mmol A1) was
added HMDS (150 mmol). The reaction was carried out as
described in Example 8. The filtrate contained 93°s of the
original aluminum value. The resulting siloxy-MAO solution
was found to be very active in ethylene polymerization (Table
1) .
Example 10
A MAO solution in toluene (272 mmol A1) was placed
in a reaction flask. HMDS (204 mmol) was slowly added from a
syringe. The reaction was carried out as described in
Example 8. The resulting filtrate contained about 82~ of the
original aluminum value. A significant reduction in the
trimethyl-aluminum (TMA) content (from 30~ TMA to 13~ TMA)
was observed for this product.
The product in conjunction with zirconocene
dichloride is highly active in ethylene polymerization (Table
1) .
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2~.I2965
Example 11
A solution of MAO in toluene (272 mmol A1) was
treated with HMDS (272 mmol). The reaction was carried out
as described in Example 8. About 86% of the original
aluminum value was recovered after filtration. The liquid
product was found to be very active in ethylene polymer-
ization (Table 1).
Example 12
MAO solution (194 mmol A1) was allowed to react
with hexaethyldisiloxane (HEDS, 38.8 mmol). The reaction was
carried out as described in Example 8. The resulting
filtrate contained 79% of the original aluminum value.
A portion of the filtrate was concentrated under
vacuum to give an oily product.
Example 13
A solution of isobutylaluminoxane (IBAO, 109 mmol
A1) in cyclohexane was treated with HMDS (27 mmol). The
mixture was stirred at room temperature for about 2 hours and
then heated (oil bath) at 100°C for another 10 hours. The
clear solution was concentrated under vacuum to give a thick
oily product. Ordinarily, a solid product would have
resulted after similar treatment of the original IBAO
solution. H-1 NMR showed broad peaks from 0.2 to 0.4 ppm
which is attributable to the siloxy-aluminoxane group. All
the other IBAO peaks are still present.
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213.29fi5
Pol3rmerization
Ethylene polymerization was conducted in a Parr
reactor (600 mL) equipped with a cooling coil, magnetic
stirrer, pressure gauge and a gas inlet. The catalyst
system, siloxy-MAO and zirconocene dichloride, are dissolved
in toluene (300 mL). The loading was done in a dry-box after
which the reactor was assembled in a well vented hood.
Ethylene was passed into the reactor at 60 psi for 10 minutes
while the temperature was maintained at about 90°C.
After cooling down to room temperature, the reactor
contents were poured into a beaker where an equal volume of
methanol was added to destroy the catalyst system. The
polyethylene was collected by filtration and then dried in a
vacuum oven.
Examples 14 and 15
Solid samples obtained from Examples 1 and 5 were
separately employed in conjunction with zirconocene
dichloride to conduct ethylene polymerization tests as
described above. Results are shown in Table 1.
Examples 16 to 19
Toluene samples of the siloxy-aluminoxanes obtained
respectively from Examples 8 to 11 were separately employed
in the presence of zirconium dichloride to conduct ethylene
polymerization as described above. Results are shown in
Table 1.
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211296
Comparison
A comparative polymerization was carried out using
regular methylaluminoxane (MAO) solution in toluene (9.4 wt.
% A1) in conjunction with zirconocene dichloride without the
addition of disiloxane. The results are shown in Table 1.
Table 1 shows that no significant additional
activity was gained as the molar ratio of HMDS was increased.
However, the data in this table show a notable increase
(about 50%) in the activity of the siloxy-MAO derivatives as
compared to the regular MAO under similar conditions.
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211965
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- 14 -
